The phenomenal growth of electronic commerce has resulted in a multitude of new applications, including the hosting, conducting and managing of remote conferences. The ability to conference with other individuals makes consultations prompt, with less travel and superior interactive experience resulting in better decision-making. Typically, conferencing includes not mere audio and video connections, but also the ability to work on documents and projects, share applications, and post stuff on blackboards and communicate via email. These latter modes of conferencing require data transfer as opposed to a stream of video and audio signals. Many software packages, including “NETMEETING™” by “MICROSOFT®” are being marketed and continuously improved to meet this growing and maturing market.
A number of standards have been developed to facilitate interoperability and efficiency between different types of operating systems, platforms, and applications that may be connected to the Internet or Intranets. The conferencing standards may be thought of as representing two rather different approaches. On one hand there are conferencing connections made by direct interactions with known parties with a centralized control of the conference. On the other hand there is a decentralized conferencing ability with connections made via, potentially, unknown intermediaries. The widely used H.323 suite of standards is quickly becoming the preferred standard for video and audio conferencing and represents decentralized conferencing. In contrast, exchange of data, as opposed to audio/video signals, is usually conducted in compliance with the T.120 set of standards which have a centralized control.
These two standards differ in the Quality of Service (QoS) in so far that H.323 utilizes “best attempt” assurances in facilitating packet based audio/video communications while T.120 uses the “error free” guarantees. There are further differences between the standards exemplified in the possible conference topologies, set up, and management of conferences. In particular, H.323 recognizes and uses ‘Gatekeepers’, ‘Gateways’ and permits implementation of a Multipoint Control Unit (MCU) in two modules, viz., a Multipoint Controller (MC) and a Multipoint Processor (MP). T.120, on the other hand, uses a Multipoint Communication Service (MCS) and Generic Conference Control (GCC) to implement conference topologies and communication flow, including provisions for channels that may be set up and torn down during a conference.
T.120 allows for conferences with a defined “Top Provider” (TP) node. Topologies compatible with a TP include trees, cascades, linear chains, star and their combinations. In contrast, H.323 envisages only a star topology, in which a conference host connects to a number of conference participants. In the case of T.120 , the requirement for one TP means that two conferences cannot be connected together. In other words, for a node participating in a T.120 compliant conference it is not possible to participate in another T.120 compliant conference because there is only one possible TP. In addition, T.120 allows for a TP with the final say on who joins a conference in progress, thus providing another tunable screen.
The flow of information may be visualized by viewing a T.120 conference as a number of domains defined by upward connectivity to the TP or a MCS node. This information flow, under MCS includes use of channels to send messages to all or a subset of participants in a T.120 conference. It is worth noting that a node in a T.120 conference may send data on only one channel at a time, but may receive data from several channels. Further details of the T.120 and H.323 standards may be found at www.imtc.org/standard.
Despite the obvious capabilities provided in the current conferencing products, many problems remain. Although adoption of packet based H.323 standards allowed conferencing to be easily implemented beyond local area network (LAN) environments, increased use of long distance communications using wide area networks (WAN) and the Internet requires that serious attention be paid to security issues. Many of the problems remain in the implementation of secure conferences in advantageously utilizing the advanced encryption/authentication schemes or flexible conference topologies. Flexible conference topologies and security concerns present new challenges since the Internet includes networks with varied accessibility due to the presence of firewalls, proxies and other intermediaries that may not be secure and/or seek to examine data.
Furthermore, limiting geographical or topological reach of conferencing is not desirable. For instance, a star topology for a H.323 conference allows for authentication of every participant in the conference, but is limiting in the topology and security. On the other hand, a T.120 conference cannot exchange video/audio signals while being able to send data over a broad range of topologies that admit of a TP. An additional limitation in T.120 conferences is that the TP has to approve the entry of a node to the conference. However, the TP cannot independently authenticate the identity of a new node since the authentication/encryption protocol is at a lower layer, and, typically, carried out between the node directly negotiating with the potential entrant. Typically, managing secure linkages is transparent to the application layer and even more inaccessible to other conference nodes. In other words the TP, and in case of other communications, the rest of the conference nodes, have to trust the negotiating node.
T.120 conferences differ from H.323 compliant conferences in not being cognizant of proxies, gateways and gatekeepers, thus being limited to direct negotiations with nodes. Adoption of the H.323 standards with interoperability with T.120 standards makes possible limited negotiations with a distant node with intervening proxies. Consequently, secure data conferences remain limited to direct connections between conference participants whose identities can be established and are available as participating nodes in the conference.